Control of composition during laser welding of aluminum-magnesium alloy using a plasma suppresion technique

One of the main problems of autogeneous laser welding Al-Mg alloy (Al-5083-0) is the loss of magnesium by evaporation or plasma formation resulting in welds of low tensile strength and unacceptable porosity. A method has been developed to control plasma formation during laser welding producing satisfactory welds with little or no magnesium loss of significant porosity. Porosity, magnesium loss, and bead quality are controlled by careful manipulation of experimental variables and inevitable control of plasma during laser beam. to substrate transmission by manipulation of a main gas jet in a shielding arrangement. The experiment has been carried out using a 10 kW CW-CO₂laser following a two-level factorial design to correlate the effects of these independent laser processing variables with as-welded alloy chemistry. Alloy composition was characterized quantitatively using electron probe microanalysis techniques. It was observed that magnesium loss could be minimized to as low as 0.9 percent. Radiographic examination and tensile tests revelaed that low porosity welds with strenghts at least as great as the parent material may be produced by controlling alloy composition via a specially designed inert gas shield.